This invention relates to centrifugal clutches and more particularly relates to novel and improved centrifugal clutches having high density cam members which are urged outwardly under centrifugal force in order to activate the clutching elements.
Centrifugal clutches have been developed for motorcycles utilizing one or two rows of balls or other cam members which would move outwardly in response to rotation of a drive shaft to cause the clutch plates to move into engagement with one another. However, in certain applications it was found that there is insufficient centrifugal force generated to clamp the clutch plates together without substantial slipping or without utilizing a larger size case or cover which exceeds the space allowances within stock engine cases. For example, space is at a particular premium in motorcycle clutches incorporating a manual override mechanism, such as, that set forth and described in copending application for U.S. patent Ser. No. 09/877,518 for AUTOMATIC CLUTCH WITH MANUAL OVERRIDE CONTROL MECHANISM.
Accordingly, there is a need for a cam mechanism for centrifugal clutches which can generate the necessary force to clamp the clutch plates together without substantial slipping or increasing the size of the clutch case or cover. At the same time it is desirable to provide a cam-actuating mechanism which requires a minimum of manual pressure to engage or disengage the clutch elements with a manual override mechanism while at the same time being highly sensitive to acceleration in speed to effect engagement of the clutch elements. Still further, a controlled amount of slippage may be built into the hub drive for the clutch in order to prevent damage to the drive train resulting from the application of shock loads. In addition, it may be desirable in certain applications to utilize a cover which can be secured along its outer peripheral edge to the clutch basket and to employ needle bearings between the inner hub and rear wall of the basket in order to minimize drag.
It is therefore an object of the present invention to provide for a novel and improved cam-actuating mechanism for an automatic clutch.
Another object of the present invention is to provide for a cam-actuating mechanism for centrifugal clutches which is capable of achieving clutch engagement at lower rpms while generating the necessary clamping force and avoiding slipping of the clutch plates in a simplified, efficient manner.
It is a further object of the present invention to provide in a centrifugal clutch, including those having internal manual override mechanisms, for an extremely compact cam mechanism which is capable of generating sufficient centrifugal force to clamp the clutch plates together without substantial slipping and within the same size case or cover as employed in stock or standard motorcycles.
It is a still further object of the present invention to provide an automatic clutch in which a series of high density balls are so constructed and arranged as to minimize wear and enable ease of positive engagement of the clutch members either in response to speed of rotation or manual pressure exerted through a manual override mechanism.
An additional object of the present invention is to provide in an automatic clutch for controlled slippage to prevent shock loads from being imparted through the drive train of a motorcycle.
In accordance with the present invention, a centrifugal clutch has a plurality of cam members interposed between a cover and pressure plate wherein the cam members are movable outwardly under centrifugal force to cause the pressure plate to move in a direction forcing the clutch members into clutching engagement, and cam retainer means between the pressure plate and cover for retaining the cam members in a plurality of concentric rows whereby to guide radial movement of the cam members and wherein one of the rows is staggered with respect to the other of the rows. In one form of invention, the cam members in one of the inner concentric rows are smaller than the cam members in other of the concentric rows and the retainer means are defined by a plurality of indented cam faces which define the concentric rows in the cover and wherein each of the cam faces includes a ramp inclining radially outwardly in a direction toward the pressure plate. The pressure plate may be correspondingly formed with cam faces aligned with the cam faces in the cover to define complementary pairs of cam faces, each of which receives one of the cam members therebetween. The space required to house the cam members is reduced by employing high density balls as the cam members which are composed of a material, such as, tungsten carbide and when arranged in multiple rows as described are sensitive to slight increases in speed of rotation of the clutch to force the clutch members into clutching engagement; and similarly a minimum of manual pressure is required of a manual override mechanism to force the cam members into and out of clutching engagement. In this relation, the compact cam-actuating mechanism enables utilization of a manual override mechanism internally of the clutch without increasing the overall size of the clutch and enable the clutch to be substituted for existing standard or stock motorcycle clutches.
Among other features of the present invention is to employ frictional control means between the clutch housing and hub to prevent shock loads from being transferred to the drive train or transmission when the clutch members remain in non-slipping engagement with one another. Another feature is to provide for circumferentially spaced bearings between the end wall of the clutch housing and inner hub when a thrust washer is mounted between the gear and inner hub to prevent galling or seizing up of the thrust washer particularly in the absence of lubrication between the thrust washer housing.
There has been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject matter of the claims appended hereto. In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting. As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying but the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.